Pacemaker Timing
Part I
Pacemaker Timing
Objectives:
Describe expected pacemaker function based on
the NBG code
Interpret intervals comprising single and dual
chamber timing
Recognize various modes of dual chamber device
operation from lower to upper rate behaviors
Calculate upper rate behavior based on
programmed parameters
Identify therapy specific device operations when
presented on patient ECG
Timing Intervals Are Expressed
in Milliseconds
One millisecond = 1 / 1,000 of a second
Converting Rates to Intervals
and Vice Versa
Rate to interval (ms):
– 60,000/rate (in bpm) = interval (in milliseconds)
– Example: 60,000/100 bpm = 600 milliseconds
Interval to rate (bpm):
– 60,000/interval (in milliseconds) = rate (bpm)
– Example: 60,000/500 ms = 120 bpm
NBG Code Review
I
Chamber
Paced
II
Chamber
Sensed
III
Response
to Sensing
IV
Programmable
Functions/Rate
Modulation
V: Ventricle
V: Ventricle
T: Triggered
P: Simple
programmable
P: Pace
A: Atrium
A: Atrium
I: Inhibited
M: Multiprogrammable
S: Shock
D: Dual (A+V)
D: Dual (A+V) D: Dual (T+I)
C: Communicating
D: Dual (P+S)
O: None
O: None
R: Rate modulating
O: None
S: Single
S: Single
(A or V)
(A or V)
O: None
O: None
V
Antitachy
Function(s)
Single-Chamber Timing
Single Chamber Timing Terminology
Lower rate
Refractory period
Blanking period
Upper rate
Lower Rate Interval
Defines the lowest rate the pacemaker will pace
Lower Rate Interval
VP
VP
VVI / 60
Refractory Period
Interval initiated by a paced or sensed event
Designed to prevent inhibition by cardiac or
non-cardiac events
Lower Rate Interval
VP
Refractory Period
VP
VVI / 60
Blanking Period
The first portion of the refractory period
Pacemaker is “blind” to any activity
Designed to prevent oversensing pacing stimulus
Lower Rate Interval
VP
Blanking Period
Refractory Period
VP
VVI / 60
Upper Sensor Rate Interval
Defines the shortest interval (highest rate) the pacemaker
can pace as dictated by the sensor (AAIR, VVIR modes)
Lower Rate Interval
Upper Sensor Rate
Interval
VP
Blanking Period
Refractory Period
VP
VVIR / 60 / 120
Single Chamber Mode Examples
VOO Mode
Asynchronous pacing delivers output regardless of
intrinsic activity
Lower Rate Interval
VP
Blanking Period
VOO / 60
VP
VVI Mode
Pacing inhibited with intrinsic activity
Lower Rate Interval
{
VP
Blanking/Refractory
VVI / 60
VS
VP
VVIR
Pacing at the sensor-indicated rate
Lower Rate
Upper Rate Interval
(Maximum Sensor Rate)
VP
VP
Refractory/Blanking
VVIR / 60/120
Rate Responsive Pacing at the Upper Sensor Rate
AAIR
Atrial-based pacing allows the normal A-V activation
sequence to occur
Lower Rate Interval
Upper Rate Interval
(maximum sensor rate)
AP
Refractory/Blanking
AAIR / 60 / 120
(No Activity)
AP
Other Single Chamber Operations
Hysteresis
Allows the rate to fall below the programmed lower
rate following an intrinsic beat
Lower Rate Interval-60 ppm
VP
VP
Hysteresis Rate-50 ppm
VS
VP
Noise Reversion
Continuous refractory sensing will cause pacing at the lower
or sensor driven rate
Lower Rate Interval
Noise Sensed
VP
VVI/60
SR
SR
SR
SR
VP
Dual-Chamber Timing
Benefits of Dual Chamber Pacing
Provides AV synchrony
Lower incidence of atrial fibrillation
Lower risk of systemic embolism and stroke
Lower incidence of new congestive heart failure
Lower mortality and higher survival rates
Benefits of Dual-Chamber Pacing
Study
Results
Higano et al. 1990
Improved cardiac index during low level
exercise (where most patient activity occurs)
Gallik et al. 1994
Increase in LV filling
Santini et al. 1991
30% increase in resting cardiac output
Rosenqvist et al. 1991 Decrease in pulmonary wedge pressure
Increase in resting cardiac output
Sulke et al. 1992
Increase in resting cardiac output, especially
in patients with poor LV function
Decreased incidence of mitral and tricuspid
valve regurgitation
Four “Faces” of Dual Chamber Pacing
Atrial Pace, Ventricular Pace (AP/VP)
AV
AP
V-A
VP
Rate = 60 bpm / 1000 ms
A-A = 1000 ms
AV
AP
VP
V-A
Four “Faces” of Dual Chamber Pacing
Atrial Pace, Ventricular Sense (AP/VS)
AV
AP
V-A
VS
Rate = 60 ppm / 1000 ms
A-A = 1000 ms
AV
AP
VS
V-A
Four “Faces” of Dual Chamber Pacing
Atrial Sense, Ventricular Pace (AS/ VP)
AV
AS
V-A
VP
V-A
AV
AS
Rate (sinus driven) = 70 bpm / 857 ms
A-A = 857 ms
VP
Four “Faces” of Dual Chamber Pacing
Atrial Sense, Ventricular Sense (AS/VS)
AV
AS
V-A
VS
Rate (sinus driven) = 70 bpm / 857 ms
Spontaneous conduction at 150 ms
A-A = 857 ms
AV
AS
V-A
VS
Dual Chamber Timing Parameters
Lower rate
AV and VA intervals
Upper rate intervals
Refractory periods
Blanking periods
Lower Rate
The lowest rate the pacemaker will pace the atrium in
the absence of intrinsic atrial events
Lower Rate Interval
AP
DDD 60 / 120
VP
AP
VP
AV Intervals
Initiated by a paced or non-refractory sensed atrial event
– Separately programmable AV intervals – SAV /PAV
Lower Rate Interval
PAV
200 ms
AP
DDD 60 / 120
VP
SAV
170 ms
AS
VP
Atrial Escape Interval (V-A Interval)
Lower rate interval
– AV interval
V-A interval
Atrial Escape Interval (V-A Interval)
The interval initiated by a paced or sensed ventricular event
to the next atrial event
Lower Rate Interval
200 ms
AV Interval
AP
DDD 60 / 120
PAV 200 ms; V-A 800 ms
VP
800 ms
VA Interval
AP
VP
Upper Activity (Sensor) Rate
In rate responsive modes, the Upper Activity Rate provides
the limit for sensor-indicated pacing
Lower Rate Limit
Upper Activity Rate Limit
PAV
DDDR 60 / 120
A-A = 500 ms
AP
VP
V-A
PAV
AP
VP
V-A
Upper Tracking Rate
The maximum rate the ventricle can be paced in response to
sensed atrial events
Lower Rate Interval
{
Upper Tracking Rate Limit
SAV
AS
VA
VP
DDDR 60 / 100 (upper tracking rate)
Sinus rate: 100 bpm
SAV
AS
VP
VA
Refractory Periods
VRP and PVARP are initiated by sensed or paced
ventricular events
– The VRP is intended to prevent self-inhibition such
as sensing of T-waves
– The PVARP is intended primarily to prevent sensing
of retrograde P waves
A-V Interval
(Atrial Refractory)
Ventricular Refractory Period
(VRP)
AP
Post Ventricular Atrial
Refractory Period (PVARP)
VP
Blanking Periods
First portion of the refractory period-sensing is disabled
AP
AP
VP
Atrial Blanking
(Nonprogrammable)
Post Ventricular Atrial
Blanking (PVAB)
Post Atrial Ventricular
Blanking
Ventricular Blanking
(Nonprogrammable)
General Medtronic Pacemaker Disclaimer
INDICATIONS
Medtronic pacemakers are indicated for rate adaptive pacing in patients who may benefit from increased pacing rates concurrent with increases in activity (Thera, Thera-i,
Prodigy, Preva and Medtronic.Kappa 700 Series) or increases in activity and/or minute ventilation (Medtronic.Kappa 400 Series).
Medtronic pacemakers are also indicated for dual chamber and atrial tracking modes in patients who may benefit from maintenance of AV synchrony. Dual chamber modes
are specifically indicated for treatment of conduction disorders that require restoration of both rate and AV synchrony, which include various degrees of AV block to maintain
the atrial contribution to cardiac output and VVI intolerance (e.g., pacemaker syndrome) in the presence of persistent sinus rhythm.
9790 Programmer
The Medtronic 9790 Programmers are portable, microprocessor based instruments used to program Medtronic implantable devices.
9462
The Model 9462 Remote Assistant™ is intended for use in combination with a Medtronic implantable pacemaker with Remote Assistant diagnostic capabilities.
CONTRAINDICATIONS
Medtronic pacemakers are contraindicated for the following applications:

Dual chamber atrial pacing in patients with chronic refractory atrial tachyarrhythmias.

Asynchronous pacing in the presence (or likelihood) of competitive paced and intrinsic rhythms.

Unipolar pacing for patients with an implanted cardioverter-defibrillator because it may cause unwanted delivery or inhibition of ICD therapy.

Medtronic.Kappa 400 Series pacemakers are contraindicated for use with epicardial leads and with abdominal implantation.
WARNINGS/PRECAUTIONS
Pacemaker patients should avoid sources of magnetic resonance imaging, diathermy, high sources of radiation, electrosurgical cautery, external defibrillation, lithotripsy, and
radiofrequency ablation to avoid electrical reset of the device, inappropriate sensing and/or therapy.
9462
Operation of the Model 9462 Remote Assistant™ Cardiac Monitor near sources of electromagnetic interference, such as cellular phones, computer monitors, etc. may
adversely affect the performance of this device.
See the appropriate technical manual for detailed information regarding indications, contraindications, warnings, and precautions.
Caution: Federal law (U.S.A.) restricts this device to sale by or on the order of a physician.
Medtronic Leads
For Indications, Contraindications, Warnings, and Precautions for Medtronic Leads, please
refer to the appropriate Leads Technical Manual or call your local Medtronic Representative.
Caution: Federal law restricts this device to sale by or on the order of a Physician.
Note:
This presentation is provided for general educational purposes only and should not be
considered the exclusive source for this type of information. At all times, it is the professional
responsibility of the practitioner to exercise independent clinical judgment in a particular
situation.
Continued in
Pacemaker Timing
Parts II and III